/*
 * Copyright (c) 1994, 2016, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
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 *
 */

package java.lang;

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.PrivilegedAction;
import java.util.Map;
import java.util.HashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.LockSupport;

import sun.nio.ch.Interruptible;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
import sun.security.util.SecurityConstants;


/**
 * A <i>thread</i> is a thread of execution in a program. The Java
 * Virtual Machine allows an application to have multiple threads of
 * execution running concurrently.
 * <p>
 * Every thread has a priority. Threads with higher priority are
 * executed in preference to threads with lower priority. Each thread
 * may or may not also be marked as a daemon. When code running in
 * some thread creates a new <code>Thread</code> object, the new
 * thread has its priority initially set equal to the priority of the
 * creating thread, and is a daemon thread if and only if the
 * creating thread is a daemon.
 * <p>
 * When a Java Virtual Machine starts up, there is usually a single
 * non-daemon thread (which typically calls the method named
 * <code>main</code> of some designated class). The Java Virtual
 * Machine continues to execute threads until either of the following
 * occurs:
 * <ul>
 * <li>The <code>exit</code> method of class <code>Runtime</code> has been
 *     called and the security manager has permitted the exit operation
 *     to take place.
 * <li>All threads that are not daemon threads have died, either by
 *     returning from the call to the <code>run</code> method or by
 *     throwing an exception that propagates beyond the <code>run</code>
 *     method.
 * </ul>
 * <p>
 * There are two ways to create a new thread of execution. One is to
 * declare a class to be a subclass of <code>Thread</code>. This
 * subclass should override the <code>run</code> method of class
 * <code>Thread</code>. An instance of the subclass can then be
 * allocated and started. For example, a thread that computes primes
 * larger than a stated value could be written as follows:
 * <hr><blockquote><pre>
 *     class PrimeThread extends Thread {
 *         long minPrime;
 *         PrimeThread(long minPrime) {
 *             this.minPrime = minPrime;
 *         }
 *
 *         public void run() {
 *             // compute primes larger than minPrime
 *             &nbsp;.&nbsp;.&nbsp;.
 *         }
 *     }
 * </pre></blockquote><hr>
 * <p>
 * The following code would then create a thread and start it running:
 * <blockquote><pre>
 *     PrimeThread p = new PrimeThread(143);
 *     p.start();
 * </pre></blockquote>
 * <p>
 * The other way to create a thread is to declare a class that
 * implements the <code>Runnable</code> interface. That class then
 * implements the <code>run</code> method. An instance of the class can
 * then be allocated, passed as an argument when creating
 * <code>Thread</code>, and started. The same example in this other
 * style looks like the following:
 * <hr><blockquote><pre>
 *     class PrimeRun implements Runnable {
 *         long minPrime;
 *         PrimeRun(long minPrime) {
 *             this.minPrime = minPrime;
 *         }
 *
 *         public void run() {
 *             // compute primes larger than minPrime
 *             &nbsp;.&nbsp;.&nbsp;.
 *         }
 *     }
 * </pre></blockquote><hr>
 * <p>
 * The following code would then create a thread and start it running:
 * <blockquote><pre>
 *     PrimeRun p = new PrimeRun(143);
 *     new Thread(p).start();
 * </pre></blockquote>
 * <p>
 * Every thread has a name for identification purposes. More than
 * one thread may have the same name. If a name is not specified when
 * a thread is created, a new name is generated for it.
 * <p>
 * Unless otherwise noted, passing a {@code null} argument to a constructor
 * or method in this class will cause a {@link NullPointerException} to be
 * thrown.
 *
 * @author unascribed
 * @see Runnable
 * @see Runtime#exit(int)
 * @see #run()
 * @see #stop()
 * @since JDK1.0
 */
public class Thread implements Runnable
{
	/* Make sure registerNatives is the first thing <clinit> does. */
	private static native void registerNatives();

	static
	{
		registerNatives();
	}

	private volatile String name;
	private int priority;
	private Thread threadQ;
	private long eetop;

	/* Whether or not to single_step this thread. */
	private boolean single_step;

	/* Whether or not the thread is a daemon thread. */
	private boolean daemon = false;

	/* JVM state */
	private boolean stillborn = false;

	/* What will be run. */
	private Runnable target;

	/* The group of this thread */
	private ThreadGroup group;

	/* The context ClassLoader for this thread */
	private ClassLoader contextClassLoader;

	/* The inherited AccessControlContext of this thread */
	private AccessControlContext inheritedAccessControlContext;

	/* For autonumbering anonymous threads. */
	private static int threadInitNumber;

	private static synchronized int nextThreadNum()
	{
		return threadInitNumber++;
	}

	/* ThreadLocal values pertaining to this thread. This map is maintained
	 * by the ThreadLocal class. */ ThreadLocal.ThreadLocalMap threadLocals = null;

	/*
	 * InheritableThreadLocal values pertaining to this thread. This map is
	 * maintained by the InheritableThreadLocal class.
	 */ ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;

	/*
	 * The requested stack size for this thread, or 0 if the creator did
	 * not specify a stack size.  It is up to the VM to do whatever it
	 * likes with this number; some VMs will ignore it.
	 */
	private long stackSize;

	/*
	 * JVM-private state that persists after native thread termination.
	 */
	private long nativeParkEventPointer;

	/*
	 * Thread ID
	 */
	private long tid;

	/* For generating thread ID */
	private static long threadSeqNumber;

	/* Java thread status for tools,
	 * initialized to indicate thread 'not yet started'
	 */

	private volatile int threadStatus = 0;


	private static synchronized long nextThreadID()
	{
		return ++threadSeqNumber;
	}

	/**
	 * The argument supplied to the current call to
	 * java.util.concurrent.locks.LockSupport.park.
	 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
	 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
	 */
	volatile Object parkBlocker;

	/* The object in which this thread is blocked in an interruptible I/O
	 * operation, if any.  The blocker's interrupt method should be invoked
	 * after setting this thread's interrupt status.
	 */
	private volatile Interruptible blocker;
	private final Object blockerLock = new Object();

	/* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code
	 */
	void blockedOn(Interruptible b)
	{
		synchronized (blockerLock)
		{
			blocker = b;
		}
	}

	/**
	 * 最小 优先级
	 * The minimum priority that a thread can have.
	 */
	public final static int MIN_PRIORITY = 1;

	/**
	 * 默认 优先级
	 * The default priority that is assigned to a thread.
	 */
	public final static int NORM_PRIORITY = 5;

	/**
	 * 最大 优先级
	 * The maximum priority that a thread can have.
	 */
	public final static int MAX_PRIORITY = 10;

	/**
	 * Returns a reference to the currently executing thread object.
	 *
	 * @return the currently executing thread.
	 */
	public static native Thread currentThread();

	/**
	 * A hint to the scheduler that the current thread is willing to yield
	 * its current use of a processor. The scheduler is free to ignore this
	 * hint.
	 *
	 * <p> Yield is a heuristic attempt to improve relative progression
	 * between threads that would otherwise over-utilise a CPU. Its use
	 * should be combined with detailed profiling and benchmarking to
	 * ensure that it actually has the desired effect.
	 *
	 * <p> It is rarely appropriate to use this method. It may be useful
	 * for debugging or testing purposes, where it may help to reproduce
	 * bugs due to race conditions. It may also be useful when designing
	 * concurrency control constructs such as the ones in the
	 * {@link java.util.concurrent.locks} package.
	 */
	public static native void yield();

	/**
	 * Causes the currently executing thread to sleep (temporarily cease
	 * execution) for the specified number of milliseconds, subject to
	 * the precision and accuracy of system timers and schedulers. The thread
	 * does not lose ownership of any monitors.
	 *
	 * @param millis the length of time to sleep in milliseconds
	 * @throws IllegalArgumentException if the value of {@code millis} is negative
	 * @throws InterruptedException     if any thread has interrupted the current thread. The
	 *                                  <i>interrupted status</i> of the current thread is
	 *                                  cleared when this exception is thrown.
	 */
	public static native void sleep(long millis) throws InterruptedException;

	/**
	 * Causes the currently executing thread to sleep (temporarily cease
	 * execution) for the specified number of milliseconds plus the specified
	 * number of nanoseconds, subject to the precision and accuracy of system
	 * timers and schedulers. The thread does not lose ownership of any
	 * monitors.
	 *
	 * @param millis the length of time to sleep in milliseconds
	 * @param nanos  {@code 0-999999} additional nanoseconds to sleep
	 * @throws IllegalArgumentException if the value of {@code millis} is negative, or the value of
	 *                                  {@code nanos} is not in the range {@code 0-999999}
	 * @throws InterruptedException     if any thread has interrupted the current thread. The
	 *                                  <i>interrupted status</i> of the current thread is
	 *                                  cleared when this exception is thrown.
	 */
	public static void sleep(long millis, int nanos) throws InterruptedException
	{
		if (millis < 0)
		{
			throw new IllegalArgumentException("timeout value is negative");
		}

		if (nanos < 0 || nanos > 999999)
		{
			throw new IllegalArgumentException("nanosecond timeout value out of range");
		}

		if (nanos >= 500000 || (nanos != 0 && millis == 0))
		{
			millis++;
		}

		sleep(millis);
	}

	/**
	 * Initializes a Thread with the current AccessControlContext.
	 *
	 * @see #init(ThreadGroup, Runnable, String, long, AccessControlContext, boolean)
	 */
	private void init(ThreadGroup g, Runnable target, String name, long stackSize)
	{
		init(g, target, name, stackSize, null, true);
	}

	/**
	 * Initializes a Thread.
	 *
	 * @param g                   the Thread group
	 * @param target              the object whose run() method gets called
	 * @param name                the name of the new Thread
	 * @param stackSize           the desired stack size for the new thread, or
	 *                            zero to indicate that this parameter is to be ignored.
	 * @param acc                 the AccessControlContext to inherit, or
	 *                            AccessController.getContext() if null
	 * @param inheritThreadLocals if {@code true}, inherit initial values for
	 *                            inheritable thread-locals from the constructing thread
	 */
	private void init(ThreadGroup g, Runnable target, String name, long stackSize, AccessControlContext acc, boolean inheritThreadLocals)
	{
		if (name == null)
		{
			throw new NullPointerException("name cannot be null");
		}

		this.name = name;

		Thread parent = currentThread();
		SecurityManager security = System.getSecurityManager();
		if (g == null)
		{
			/* Determine if it's an applet or not */

            /* If there is a security manager, ask the security manager
               what to do. */
			if (security != null)
			{
				g = security.getThreadGroup();
			}

            /* If the security doesn't have a strong opinion of the matter
               use the parent thread group. */
			if (g == null)
			{
				g = parent.getThreadGroup();
			}
		}

        /* checkAccess regardless of whether or not threadgroup is
           explicitly passed in. */
		g.checkAccess();

		/*
		 * Do we have the required permissions?
		 */
		if (security != null)
		{
			if (isCCLOverridden(getClass()))
			{
				security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
			}
		}

		g.addUnstarted();

		this.group = g;
		this.daemon = parent.isDaemon();
		this.priority = parent.getPriority();
		if (security == null || isCCLOverridden(parent.getClass()))
			this.contextClassLoader = parent.getContextClassLoader();
		else this.contextClassLoader = parent.contextClassLoader;
		this.inheritedAccessControlContext = acc != null ? acc : AccessController.getContext();
		this.target = target;
		setPriority(priority);
		if (inheritThreadLocals && parent.inheritableThreadLocals != null)
			this.inheritableThreadLocals = ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
		/* Stash the specified stack size in case the VM cares */
		this.stackSize = stackSize;

		/* Set thread ID */
		tid = nextThreadID();
	}

	/**
	 * Throws CloneNotSupportedException as a Thread can not be meaningfully
	 * cloned. Construct a new Thread instead.
	 *
	 * @throws CloneNotSupportedException always
	 */
	@Override
	protected Object clone() throws CloneNotSupportedException
	{
		throw new CloneNotSupportedException();
	}

	/**
	 * Allocates a new {@code Thread} object. This constructor has the same
	 * effect as {@linkplain #Thread(ThreadGroup, Runnable, String) Thread}
	 * {@code (null, null, gname)}, where {@code gname} is a newly generated
	 * name. Automatically generated names are of the form
	 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
	 */
	public Thread()
	{
		init(null, null, "Thread-" + nextThreadNum(), 0);
	}

	/**
	 * Allocates a new {@code Thread} object. This constructor has the same
	 * effect as {@linkplain #Thread(ThreadGroup, Runnable, String) Thread}
	 * {@code (null, target, gname)}, where {@code gname} is a newly generated
	 * name. Automatically generated names are of the form
	 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
	 *
	 * @param target the object whose {@code run} method is invoked when this thread
	 *               is started. If {@code null}, this classes {@code run} method does
	 *               nothing.
	 */
	public Thread(Runnable target)
	{
		init(null, target, "Thread-" + nextThreadNum(), 0);
	}

	/**
	 * Creates a new Thread that inherits the given AccessControlContext.
	 * This is not a public constructor.
	 */
	Thread(Runnable target, AccessControlContext acc)
	{
		init(null, target, "Thread-" + nextThreadNum(), 0, acc, false);
	}

	/**
	 * Allocates a new {@code Thread} object. This constructor has the same
	 * effect as {@linkplain #Thread(ThreadGroup, Runnable, String) Thread}
	 * {@code (group, target, gname)} ,where {@code gname} is a newly generated
	 * name. Automatically generated names are of the form
	 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
	 *
	 * @param group  the thread group. If {@code null} and there is a security
	 *               manager, the group is determined by {@linkplain
	 *               SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
	 *               If there is not a security manager or {@code
	 *               SecurityManager.getThreadGroup()} returns {@code null}, the group
	 *               is set to the current thread's thread group.
	 * @param target the object whose {@code run} method is invoked when this thread
	 *               is started. If {@code null}, this thread's run method is invoked.
	 * @throws SecurityException if the current thread cannot create a thread in the specified
	 *                           thread group
	 */
	public Thread(ThreadGroup group, Runnable target)
	{
		init(group, target, "Thread-" + nextThreadNum(), 0);
	}

	/**
	 * Allocates a new {@code Thread} object. This constructor has the same
	 * effect as {@linkplain #Thread(ThreadGroup, Runnable, String) Thread}
	 * {@code (null, null, name)}.
	 *
	 * @param name the name of the new thread
	 */
	public Thread(String name)
	{
		init(null, null, name, 0);
	}

	/**
	 * Allocates a new {@code Thread} object. This constructor has the same
	 * effect as {@linkplain #Thread(ThreadGroup, Runnable, String) Thread}
	 * {@code (group, null, name)}.
	 *
	 * @param group the thread group. If {@code null} and there is a security
	 *              manager, the group is determined by {@linkplain
	 *              SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
	 *              If there is not a security manager or {@code
	 *              SecurityManager.getThreadGroup()} returns {@code null}, the group
	 *              is set to the current thread's thread group.
	 * @param name  the name of the new thread
	 * @throws SecurityException if the current thread cannot create a thread in the specified
	 *                           thread group
	 */
	public Thread(ThreadGroup group, String name)
	{
		init(group, null, name, 0);
	}

	/**
	 * Allocates a new {@code Thread} object. This constructor has the same
	 * effect as {@linkplain #Thread(ThreadGroup, Runnable, String) Thread}
	 * {@code (null, target, name)}.
	 *
	 * @param target the object whose {@code run} method is invoked when this thread
	 *               is started. If {@code null}, this thread's run method is invoked.
	 * @param name   the name of the new thread
	 */
	public Thread(Runnable target, String name)
	{
		init(null, target, name, 0);
	}

	/**
	 * Allocates a new {@code Thread} object so that it has {@code target}
	 * as its run object, has the specified {@code name} as its name,
	 * and belongs to the thread group referred to by {@code group}.
	 *
	 * <p>If there is a security manager, its
	 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
	 * method is invoked with the ThreadGroup as its argument.
	 *
	 * <p>In addition, its {@code checkPermission} method is invoked with
	 * the {@code RuntimePermission("enableContextClassLoaderOverride")}
	 * permission when invoked directly or indirectly by the constructor
	 * of a subclass which overrides the {@code getContextClassLoader}
	 * or {@code setContextClassLoader} methods.
	 *
	 * <p>The priority of the newly created thread is set equal to the
	 * priority of the thread creating it, that is, the currently running
	 * thread. The method {@linkplain #setPriority setPriority} may be
	 * used to change the priority to a new value.
	 *
	 * <p>The newly created thread is initially marked as being a daemon
	 * thread if and only if the thread creating it is currently marked
	 * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
	 * may be used to change whether or not a thread is a daemon.
	 *
	 * @param group  the thread group. If {@code null} and there is a security
	 *               manager, the group is determined by {@linkplain
	 *               SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
	 *               If there is not a security manager or {@code
	 *               SecurityManager.getThreadGroup()} returns {@code null}, the group
	 *               is set to the current thread's thread group.
	 * @param target the object whose {@code run} method is invoked when this thread
	 *               is started. If {@code null}, this thread's run method is invoked.
	 * @param name   the name of the new thread
	 * @throws SecurityException if the current thread cannot create a thread in the specified
	 *                           thread group or cannot override the context class loader methods.
	 */
	public Thread(ThreadGroup group, Runnable target, String name)
	{
		init(group, target, name, 0);
	}

	/**
	 * Allocates a new {@code Thread} object so that it has {@code target}
	 * as its run object, has the specified {@code name} as its name,
	 * and belongs to the thread group referred to by {@code group}, and has
	 * the specified <i>stack size</i>.
	 *
	 * <p>This constructor is identical to {@link
	 * #Thread(ThreadGroup, Runnable, String)} with the exception of the fact
	 * that it allows the thread stack size to be specified.  The stack size
	 * is the approximate number of bytes of address space that the virtual
	 * machine is to allocate for this thread's stack.  <b>The effect of the
	 * {@code stackSize} parameter, if any, is highly platform dependent.</b>
	 *
	 * <p>On some platforms, specifying a higher value for the
	 * {@code stackSize} parameter may allow a thread to achieve greater
	 * recursion depth before throwing a {@link StackOverflowError}.
	 * Similarly, specifying a lower value may allow a greater number of
	 * threads to exist concurrently without throwing an {@link
	 * OutOfMemoryError} (or other internal error).  The details of
	 * the relationship between the value of the <tt>stackSize</tt> parameter
	 * and the maximum recursion depth and concurrency level are
	 * platform-dependent.  <b>On some platforms, the value of the
	 * {@code stackSize} parameter may have no effect whatsoever.</b>
	 *
	 * <p>The virtual machine is free to treat the {@code stackSize}
	 * parameter as a suggestion.  If the specified value is unreasonably low
	 * for the platform, the virtual machine may instead use some
	 * platform-specific minimum value; if the specified value is unreasonably
	 * high, the virtual machine may instead use some platform-specific
	 * maximum.  Likewise, the virtual machine is free to round the specified
	 * value up or down as it sees fit (or to ignore it completely).
	 *
	 * <p>Specifying a value of zero for the {@code stackSize} parameter will
	 * cause this constructor to behave exactly like the
	 * {@code Thread(ThreadGroup, Runnable, String)} constructor.
	 *
	 * <p><i>Due to the platform-dependent nature of the behavior of this
	 * constructor, extreme care should be exercised in its use.
	 * The thread stack size necessary to perform a given computation will
	 * likely vary from one JRE implementation to another.  In light of this
	 * variation, careful tuning of the stack size parameter may be required,
	 * and the tuning may need to be repeated for each JRE implementation on
	 * which an application is to run.</i>
	 *
	 * <p>Implementation note: Java platform implementers are encouraged to
	 * document their implementation's behavior with respect to the
	 * {@code stackSize} parameter.
	 *
	 * @param group     the thread group. If {@code null} and there is a security
	 *                  manager, the group is determined by {@linkplain
	 *                  SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
	 *                  If there is not a security manager or {@code
	 *                  SecurityManager.getThreadGroup()} returns {@code null}, the group
	 *                  is set to the current thread's thread group.
	 * @param target    the object whose {@code run} method is invoked when this thread
	 *                  is started. If {@code null}, this thread's run method is invoked.
	 * @param name      the name of the new thread
	 * @param stackSize the desired stack size for the new thread, or zero to indicate
	 *                  that this parameter is to be ignored.
	 * @throws SecurityException if the current thread cannot create a thread in the specified
	 *                           thread group
	 * @since 1.4
	 */
	public Thread(ThreadGroup group, Runnable target, String name, long stackSize)
	{
		init(group, target, name, stackSize);
	}

	/**
	 * Causes this thread to begin execution; the Java Virtual Machine
	 * calls the <code>run</code> method of this thread.
	 * <p>
	 * The result is that two threads are running concurrently: the
	 * current thread (which returns from the call to the
	 * <code>start</code> method) and the other thread (which executes its
	 * <code>run</code> method).
	 * <p>
	 * It is never legal to start a thread more than once.
	 * In particular, a thread may not be restarted once it has completed
	 * execution.
	 *
	 * @throws IllegalThreadStateException if the thread was already
	 *                                     started.
	 * @see #run()
	 * @see #stop()
	 */
	public synchronized void start()
	{
		/**
		 * This method is not invoked for the main method thread or "system"
		 * group threads created/set up by the VM. Any new functionality added
		 * to this method in the future may have to also be added to the VM.
		 *
		 * A zero status value corresponds to state "NEW".
		 */
		if (threadStatus != 0) throw new IllegalThreadStateException();

		/* Notify the group that this thread is about to be started
		 * so that it can be added to the group's list of threads
		 * and the group's unstarted count can be decremented. */
		group.add(this);

		boolean started = false;
		try
		{
			start0();
			started = true;
		} finally
		{
			try
			{
				if (!started)
				{
					group.threadStartFailed(this);
				}
			} catch (Throwable ignore)
			{
                /* do nothing. If start0 threw a Throwable then
                  it will be passed up the call stack */
			}
		}
	}

	/**
	 * 与 java 无关 调用 操作系统方法 在 jvm中处于 本地方法栈 区
	 */
	private native void start0();

	/**
	 * If this thread was constructed using a separate
	 * <code>Runnable</code> run object, then that
	 * <code>Runnable</code> object's <code>run</code> method is called;
	 * otherwise, this method does nothing and returns.
	 * <p>
	 * Subclasses of <code>Thread</code> should override this method.
	 *
	 * @see #start()
	 * @see #stop()
	 * @see #Thread(ThreadGroup, Runnable, String)
	 */
	@Override
	public void run()
	{
		if (target != null)
		{
			target.run();
		}
	}

	/**
	 * This method is called by the system to give a Thread
	 * a chance to clean up before it actually exits.
	 */
	private void exit()
	{
		if (group != null)
		{
			group.threadTerminated(this);
			group = null;
		}
		/* Aggressively null out all reference fields: see bug 4006245 */
		target = null;
		/* Speed the release of some of these resources */
		threadLocals = null;
		inheritableThreadLocals = null;
		inheritedAccessControlContext = null;
		blocker = null;
		uncaughtExceptionHandler = null;
	}

	/**
	 * Forces the thread to stop executing.
	 * <p>
	 * If there is a security manager installed, its <code>checkAccess</code>
	 * method is called with <code>this</code>
	 * as its argument. This may result in a
	 * <code>SecurityException</code> being raised (in the current thread).
	 * <p>
	 * If this thread is different from the current thread (that is, the current
	 * thread is trying to stop a thread other than itself), the
	 * security manager's <code>checkPermission</code> method (with a
	 * <code>RuntimePermission("stopThread")</code> argument) is called in
	 * addition.
	 * Again, this may result in throwing a
	 * <code>SecurityException</code> (in the current thread).
	 * <p>
	 * The thread represented by this thread is forced to stop whatever
	 * it is doing abnormally and to throw a newly created
	 * <code>ThreadDeath</code> object as an exception.
	 * <p>
	 * It is permitted to stop a thread that has not yet been started.
	 * If the thread is eventually started, it immediately terminates.
	 * <p>
	 * An application should not normally try to catch
	 * <code>ThreadDeath</code> unless it must do some extraordinary
	 * cleanup operation (note that the throwing of
	 * <code>ThreadDeath</code> causes <code>finally</code> clauses of
	 * <code>try</code> statements to be executed before the thread
	 * officially dies).  If a <code>catch</code> clause catches a
	 * <code>ThreadDeath</code> object, it is important to rethrow the
	 * object so that the thread actually dies.
	 * <p>
	 * The top-level error handler that reacts to otherwise uncaught
	 * exceptions does not print out a message or otherwise notify the
	 * application if the uncaught exception is an instance of
	 * <code>ThreadDeath</code>.
	 *
	 * @throws SecurityException if the current thread cannot
	 *                           modify this thread.
	 * @see #interrupt()
	 * @see #checkAccess()
	 * @see #run()
	 * @see #start()
	 * @see ThreadDeath
	 * @see ThreadGroup#uncaughtException(Thread, Throwable)
	 * @see SecurityManager#checkAccess(Thread)
	 * @see SecurityManager#checkPermission
	 * @deprecated This method is inherently unsafe.  Stopping a thread with
	 * Thread.stop causes it to unlock all of the monitors that it
	 * has locked (as a natural consequence of the unchecked
	 * <code>ThreadDeath</code> exception propagating up the stack).  If
	 * any of the objects previously protected by these monitors were in
	 * an inconsistent state, the damaged objects become visible to
	 * other threads, potentially resulting in arbitrary behavior.  Many
	 * uses of <code>stop</code> should be replaced by code that simply
	 * modifies some variable to indicate that the target thread should
	 * stop running.  The target thread should check this variable
	 * regularly, and return from its run method in an orderly fashion
	 * if the variable indicates that it is to stop running.  If the
	 * target thread waits for long periods (on a condition variable,
	 * for example), the <code>interrupt</code> method should be used to
	 * interrupt the wait.
	 * For more information, see
	 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
	 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
	 */
	@Deprecated
	public final void stop()
	{
		SecurityManager security = System.getSecurityManager();
		if (security != null)
		{
			checkAccess();
			if (this != Thread.currentThread())
			{
				security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
			}
		}
		// A zero status value corresponds to "NEW", it can't change to
		// not-NEW because we hold the lock.
		if (threadStatus != 0)
		{
			resume(); // Wake up thread if it was suspended; no-op otherwise
		}

		// The VM can handle all thread states
		stop0(new ThreadDeath());
	}

	/**
	 * Throws {@code UnsupportedOperationException}.
	 *
	 * @param obj ignored
	 * @deprecated This method was originally designed to force a thread to stop
	 * and throw a given {@code Throwable} as an exception. It was
	 * inherently unsafe (see {@link #stop()} for details), and furthermore
	 * could be used to generate exceptions that the target thread was
	 * not prepared to handle.
	 * For more information, see
	 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
	 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
	 */
	@Deprecated
	public final synchronized void stop(Throwable obj)
	{
		throw new UnsupportedOperationException();
	}

	/**
	 * Interrupts this thread.
	 *
	 * <p> Unless the current thread is interrupting itself, which is
	 * always permitted, the {@link #checkAccess() checkAccess} method
	 * of this thread is invoked, which may cause a {@link
	 * SecurityException} to be thrown.
	 *
	 * <p> If this thread is blocked in an invocation of the {@link
	 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
	 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
	 * class, or of the {@link #join()}, {@link #join(long)}, {@link
	 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
	 * methods of this class, then its interrupt status will be cleared and it
	 * will receive an {@link InterruptedException}.
	 *
	 * <p> If this thread is blocked in an I/O operation upon an {@link
	 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
	 * then the channel will be closed, the thread's interrupt
	 * status will be set, and the thread will receive a {@link
	 * java.nio.channels.ClosedByInterruptException}.
	 *
	 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
	 * then the thread's interrupt status will be set and it will return
	 * immediately from the selection operation, possibly with a non-zero
	 * value, just as if the selector's {@link
	 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
	 *
	 * <p> If none of the previous conditions hold then this thread's interrupt
	 * status will be set. </p>
	 *
	 * <p> Interrupting a thread that is not alive need not have any effect.
	 *
	 * @throws SecurityException if the current thread cannot modify this thread
	 * @revised 6.0
	 * @spec JSR-51
	 */
	public void interrupt()
	{
		if (this != Thread.currentThread()) checkAccess();

		synchronized (blockerLock)
		{
			Interruptible b = blocker;
			if (b != null)
			{
				interrupt0();           // Just to set the interrupt flag
				b.interrupt(this);
				return;
			}
		}
		interrupt0();
	}

	/**
	 * Tests whether the current thread has been interrupted.  The
	 * <i>interrupted status</i> of the thread is cleared by this method.  In
	 * other words, if this method were to be called twice in succession, the
	 * second call would return false (unless the current thread were
	 * interrupted again, after the first call had cleared its interrupted
	 * status and before the second call had examined it).
	 *
	 * <p>A thread interruption ignored because a thread was not alive
	 * at the time of the interrupt will be reflected by this method
	 * returning false.
	 *
	 * @return <code>true</code> if the current thread has been interrupted;
	 * <code>false</code> otherwise.
	 * @revised 6.0
	 * @see #isInterrupted()
	 */
	public static boolean interrupted()
	{
		return currentThread().isInterrupted(true);
	}

	/**
	 * Tests whether this thread has been interrupted.  The <i>interrupted
	 * status</i> of the thread is unaffected by this method.
	 *
	 * <p>A thread interruption ignored because a thread was not alive
	 * at the time of the interrupt will be reflected by this method
	 * returning false.
	 *
	 * @return <code>true</code> if this thread has been interrupted;
	 * <code>false</code> otherwise.
	 * @revised 6.0
	 * @see #interrupted()
	 */
	public boolean isInterrupted()
	{
		return isInterrupted(false);
	}

	/**
	 * Tests if some Thread has been interrupted.  The interrupted state
	 * is reset or not based on the value of ClearInterrupted that is
	 * passed.
	 */
	private native boolean isInterrupted(boolean ClearInterrupted);

	/**
	 * Throws {@link NoSuchMethodError}.
	 *
	 * @throws NoSuchMethodError always
	 * @deprecated This method was originally designed to destroy this
	 * thread without any cleanup. Any monitors it held would have
	 * remained locked. However, the method was never implemented.
	 * If if were to be implemented, it would be deadlock-prone in
	 * much the manner of {@link #suspend}. If the target thread held
	 * a lock protecting a critical system resource when it was
	 * destroyed, no thread could ever access this resource again.
	 * If another thread ever attempted to lock this resource, deadlock
	 * would result. Such deadlocks typically manifest themselves as
	 * "frozen" processes. For more information, see
	 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
	 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
	 */
	@Deprecated
	public void destroy()
	{
		throw new NoSuchMethodError();
	}

	/**
	 * Tests if this thread is alive. A thread is alive if it has
	 * been started and has not yet died.
	 *
	 * @return <code>true</code> if this thread is alive;
	 * <code>false</code> otherwise.
	 */
	public final native boolean isAlive();

	/**
	 * Suspends this thread.
	 * <p>
	 * First, the <code>checkAccess</code> method of this thread is called
	 * with no arguments. This may result in throwing a
	 * <code>SecurityException </code>(in the current thread).
	 * <p>
	 * If the thread is alive, it is suspended and makes no further
	 * progress unless and until it is resumed.
	 *
	 * @throws SecurityException if the current thread cannot modify
	 *                           this thread.
	 * @see #checkAccess
	 * @deprecated This method has been deprecated, as it is
	 * inherently deadlock-prone.  If the target thread holds a lock on the
	 * monitor protecting a critical system resource when it is suspended, no
	 * thread can access this resource until the target thread is resumed. If
	 * the thread that would resume the target thread attempts to lock this
	 * monitor prior to calling <code>resume</code>, deadlock results.  Such
	 * deadlocks typically manifest themselves as "frozen" processes.
	 * For more information, see
	 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
	 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
	 */
	@Deprecated
	public final void suspend()
	{
		checkAccess();
		suspend0();
	}

	/**
	 * Resumes a suspended thread.
	 * <p>
	 * First, the <code>checkAccess</code> method of this thread is called
	 * with no arguments. This may result in throwing a
	 * <code>SecurityException</code> (in the current thread).
	 * <p>
	 * If the thread is alive but suspended, it is resumed and is
	 * permitted to make progress in its execution.
	 *
	 * @throws SecurityException if the current thread cannot modify this
	 *                           thread.
	 * @see #checkAccess
	 * @see #suspend()
	 * @deprecated This method exists solely for use with {@link #suspend},
	 * which has been deprecated because it is deadlock-prone.
	 * For more information, see
	 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
	 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
	 */
	@Deprecated
	public final void resume()
	{
		checkAccess();
		resume0();
	}

	/**
	 * Changes the priority of this thread.
	 * <p>
	 * First the <code>checkAccess</code> method of this thread is called
	 * with no arguments. This may result in throwing a
	 * <code>SecurityException</code>.
	 * <p>
	 * Otherwise, the priority of this thread is set to the smaller of
	 * the specified <code>newPriority</code> and the maximum permitted
	 * priority of the thread's thread group.
	 *
	 * @param newPriority priority to set this thread to
	 * @throws IllegalArgumentException If the priority is not in the
	 *                                  range <code>MIN_PRIORITY</code> to
	 *                                  <code>MAX_PRIORITY</code>.
	 * @throws SecurityException        if the current thread cannot modify
	 *                                  this thread.
	 * @see #getPriority
	 * @see #checkAccess()
	 * @see #getThreadGroup()
	 * @see #MAX_PRIORITY
	 * @see #MIN_PRIORITY
	 * @see ThreadGroup#getMaxPriority()
	 */
	public final void setPriority(int newPriority)
	{
		ThreadGroup g;
		checkAccess();
		if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY)
		{
			throw new IllegalArgumentException();
		}
		if ((g = getThreadGroup()) != null)
		{
			if (newPriority > g.getMaxPriority())
			{
				newPriority = g.getMaxPriority();
			}
			setPriority0(priority = newPriority);
		}
	}

	/**
	 * Returns this thread's priority.
	 *
	 * @return this thread's priority.
	 * @see #setPriority
	 */
	public final int getPriority()
	{
		return priority;
	}

	/**
	 * Changes the name of this thread to be equal to the argument
	 * <code>name</code>.
	 * <p>
	 * First the <code>checkAccess</code> method of this thread is called
	 * with no arguments. This may result in throwing a
	 * <code>SecurityException</code>.
	 *
	 * @param name the new name for this thread.
	 * @throws SecurityException if the current thread cannot modify this
	 *                           thread.
	 * @see #getName
	 * @see #checkAccess()
	 */
	public final synchronized void setName(String name)
	{
		checkAccess();
		if (name == null)
		{
			throw new NullPointerException("name cannot be null");
		}

		this.name = name;
		if (threadStatus != 0)
		{
			setNativeName(name);
		}
	}

	/**
	 * Returns this thread's name.
	 *
	 * @return this thread's name.
	 * @see #setName(String)
	 */
	public final String getName()
	{
		return name;
	}

	/**
	 * Returns the thread group to which this thread belongs.
	 * This method returns null if this thread has died
	 * (been stopped).
	 *
	 * @return this thread's thread group.
	 */
	public final ThreadGroup getThreadGroup()
	{
		return group;
	}

	/**
	 * Returns an estimate of the number of active threads in the current
	 * thread's {@linkplain java.lang.ThreadGroup thread group} and its
	 * subgroups. Recursively iterates over all subgroups in the current
	 * thread's thread group.
	 *
	 * <p> The value returned is only an estimate because the number of
	 * threads may change dynamically while this method traverses internal
	 * data structures, and might be affected by the presence of certain
	 * system threads. This method is intended primarily for debugging
	 * and monitoring purposes.
	 *
	 * @return an estimate of the number of active threads in the current
	 * thread's thread group and in any other thread group that
	 * has the current thread's thread group as an ancestor
	 */
	public static int activeCount()
	{
		return currentThread().getThreadGroup().activeCount();
	}

	/**
	 * Copies into the specified array every active thread in the current
	 * thread's thread group and its subgroups. This method simply
	 * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
	 * method of the current thread's thread group.
	 *
	 * <p> An application might use the {@linkplain #activeCount activeCount}
	 * method to get an estimate of how big the array should be, however
	 * <i>if the array is too short to hold all the threads, the extra threads
	 * are silently ignored.</i>  If it is critical to obtain every active
	 * thread in the current thread's thread group and its subgroups, the
	 * invoker should verify that the returned int value is strictly less
	 * than the length of {@code tarray}.
	 *
	 * <p> Due to the inherent race condition in this method, it is recommended
	 * that the method only be used for debugging and monitoring purposes.
	 *
	 * @param tarray an array into which to put the list of threads
	 * @return the number of threads put into the array
	 * @throws SecurityException if {@link java.lang.ThreadGroup#checkAccess} determines that
	 *                           the current thread cannot access its thread group
	 */
	public static int enumerate(Thread tarray[])
	{
		return currentThread().getThreadGroup().enumerate(tarray);
	}

	/**
	 * Counts the number of stack frames in this thread. The thread must
	 * be suspended.
	 *
	 * @return the number of stack frames in this thread.
	 * @throws IllegalThreadStateException if this thread is not
	 *                                     suspended.
	 * @deprecated The definition of this call depends on {@link #suspend},
	 * which is deprecated.  Further, the results of this call
	 * were never well-defined.
	 */
	@Deprecated
	public native int countStackFrames();

	/**
	 * Waits at most {@code millis} milliseconds for this thread to
	 * die. A timeout of {@code 0} means to wait forever.
	 *
	 * <p> This implementation uses a loop of {@code this.wait} calls
	 * conditioned on {@code this.isAlive}. As a thread terminates the
	 * {@code this.notifyAll} method is invoked. It is recommended that
	 * applications not use {@code wait}, {@code notify}, or
	 * {@code notifyAll} on {@code Thread} instances.
	 *
	 * @param millis the time to wait in milliseconds
	 * @throws IllegalArgumentException if the value of {@code millis} is negative
	 * @throws InterruptedException     if any thread has interrupted the current thread. The
	 *                                  <i>interrupted status</i> of the current thread is
	 *                                  cleared when this exception is thrown.
	 */
	public final synchronized void join(long millis) throws InterruptedException
	{
		long base = System.currentTimeMillis();
		long now = 0;

		if (millis < 0)
		{
			throw new IllegalArgumentException("timeout value is negative");
		}

		if (millis == 0)
		{
			while (isAlive())
			{
				wait(0);
			}
		} else
		{
			while (isAlive())
			{
				long delay = millis - now;
				if (delay <= 0)
				{
					break;
				}
				wait(delay);
				now = System.currentTimeMillis() - base;
			}
		}
	}

	/**
	 * Waits at most {@code millis} milliseconds plus
	 * {@code nanos} nanoseconds for this thread to die.
	 *
	 * <p> This implementation uses a loop of {@code this.wait} calls
	 * conditioned on {@code this.isAlive}. As a thread terminates the
	 * {@code this.notifyAll} method is invoked. It is recommended that
	 * applications not use {@code wait}, {@code notify}, or
	 * {@code notifyAll} on {@code Thread} instances.
	 *
	 * @param millis the time to wait in milliseconds
	 * @param nanos  {@code 0-999999} additional nanoseconds to wait
	 * @throws IllegalArgumentException if the value of {@code millis} is negative, or the value
	 *                                  of {@code nanos} is not in the range {@code 0-999999}
	 * @throws InterruptedException     if any thread has interrupted the current thread. The
	 *                                  <i>interrupted status</i> of the current thread is
	 *                                  cleared when this exception is thrown.
	 */
	public final synchronized void join(long millis, int nanos) throws InterruptedException
	{

		if (millis < 0)
		{
			throw new IllegalArgumentException("timeout value is negative");
		}

		if (nanos < 0 || nanos > 999999)
		{
			throw new IllegalArgumentException("nanosecond timeout value out of range");
		}

		if (nanos >= 500000 || (nanos != 0 && millis == 0))
		{
			millis++;
		}

		join(millis);
	}

	/**
	 * 等待此线程 结束
	 * Waits for this thread to die.
	 *
	 * <p> An invocation of this method behaves in exactly the same
	 * way as the invocation
	 *
	 * <blockquote>
	 * {@linkplain #join(long) join}{@code (0)}
	 * </blockquote>
	 *
	 * @throws InterruptedException if any thread has interrupted the current thread. The
	 *                              <i>interrupted status</i> of the current thread is
	 *                              cleared when this exception is thrown.
	 */
	public final void join() throws InterruptedException
	{
		join(0);
	}

	/**
	 * Prints a stack trace of the current thread to the standard error stream.
	 * This method is used only for debugging.
	 *
	 * @see Throwable#printStackTrace()
	 */
	public static void dumpStack()
	{
		new Exception("Stack trace").printStackTrace();
	}

	/**
	 * Marks this thread as either a {@linkplain #isDaemon daemon} thread
	 * or a user thread. The Java Virtual Machine exits when the only
	 * threads running are all daemon threads.
	 *
	 * <p> This method must be invoked before the thread is started.
	 *
	 * @param on if {@code true}, marks this thread as a daemon thread
	 * @throws IllegalThreadStateException if this thread is {@linkplain #isAlive alive}
	 * @throws SecurityException           if {@link #checkAccess} determines that the current
	 *                                     thread cannot modify this thread
	 */
	public final void setDaemon(boolean on)
	{
		checkAccess();
		if (isAlive())
		{
			throw new IllegalThreadStateException();
		}
		daemon = on;
	}

	/**
	 * Tests if this thread is a daemon thread.
	 *
	 * @return <code>true</code> if this thread is a daemon thread;
	 * <code>false</code> otherwise.
	 * @see #setDaemon(boolean)
	 */
	public final boolean isDaemon()
	{
		return daemon;
	}

	/**
	 * Determines if the currently running thread has permission to
	 * modify this thread.
	 * <p>
	 * If there is a security manager, its <code>checkAccess</code> method
	 * is called with this thread as its argument. This may result in
	 * throwing a <code>SecurityException</code>.
	 *
	 * @throws SecurityException if the current thread is not allowed to
	 *                           access this thread.
	 * @see SecurityManager#checkAccess(Thread)
	 */
	public final void checkAccess()
	{
		SecurityManager security = System.getSecurityManager();
		if (security != null)
		{
			security.checkAccess(this);
		}
	}

	/**
	 * Returns a string representation of this thread, including the
	 * thread's name, priority, and thread group.
	 *
	 * @return a string representation of this thread.
	 */
	public String toString()
	{
		ThreadGroup group = getThreadGroup();
		if (group != null)
		{
			return "Thread[" + getName() + "," + getPriority() + "," + group.getName() + "]";
		} else
		{
			return "Thread[" + getName() + "," + getPriority() + "," + "" + "]";
		}
	}

	/**
	 * Returns the context ClassLoader for this Thread. The context
	 * ClassLoader is provided by the creator of the thread for use
	 * by code running in this thread when loading classes and resources.
	 * If not {@linkplain #setContextClassLoader set}, the default is the
	 * ClassLoader context of the parent Thread. The context ClassLoader of the
	 * primordial thread is typically set to the class loader used to load the
	 * application.
	 *
	 * <p>If a security manager is present, and the invoker's class loader is not
	 * {@code null} and is not the same as or an ancestor of the context class
	 * loader, then this method invokes the security manager's {@link
	 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
	 * method with a {@link RuntimePermission RuntimePermission}{@code
	 * ("getClassLoader")} permission to verify that retrieval of the context
	 * class loader is permitted.
	 *
	 * @return the context ClassLoader for this Thread, or {@code null}
	 * indicating the system class loader (or, failing that, the
	 * bootstrap class loader)
	 * @throws SecurityException if the current thread cannot get the context ClassLoader
	 * @since 1.2
	 */
	@CallerSensitive
	public ClassLoader getContextClassLoader()
	{
		if (contextClassLoader == null) return null;
		SecurityManager sm = System.getSecurityManager();
		if (sm != null)
		{
			ClassLoader.checkClassLoaderPermission(contextClassLoader, Reflection.getCallerClass());
		}
		return contextClassLoader;
	}

	/**
	 * Sets the context ClassLoader for this Thread. The context
	 * ClassLoader can be set when a thread is created, and allows
	 * the creator of the thread to provide the appropriate class loader,
	 * through {@code getContextClassLoader}, to code running in the thread
	 * when loading classes and resources.
	 *
	 * <p>If a security manager is present, its {@link
	 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
	 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code
	 * ("setContextClassLoader")} permission to see if setting the context
	 * ClassLoader is permitted.
	 *
	 * @param cl the context ClassLoader for this Thread, or null  indicating the
	 *           system class loader (or, failing that, the bootstrap class loader)
	 * @throws SecurityException if the current thread cannot set the context ClassLoader
	 * @since 1.2
	 */
	public void setContextClassLoader(ClassLoader cl)
	{
		SecurityManager sm = System.getSecurityManager();
		if (sm != null)
		{
			sm.checkPermission(new RuntimePermission("setContextClassLoader"));
		}
		contextClassLoader = cl;
	}

	/**
	 * Returns <tt>true</tt> if and only if the current thread holds the
	 * monitor lock on the specified object.
	 *
	 * <p>This method is designed to allow a program to assert that
	 * the current thread already holds a specified lock:
	 * <pre>
	 *     assert Thread.holdsLock(obj);
	 * </pre>
	 *
	 * @param obj the object on which to test lock ownership
	 * @return <tt>true</tt> if the current thread holds the monitor lock on
	 * the specified object.
	 * @throws NullPointerException if obj is <tt>null</tt>
	 * @since 1.4
	 */
	public static native boolean holdsLock(Object obj);

	private static final StackTraceElement[] EMPTY_STACK_TRACE = new StackTraceElement[0];

	/**
	 * Returns an array of stack trace elements representing the stack dump
	 * of this thread.  This method will return a zero-length array if
	 * this thread has not started, has started but has not yet been
	 * scheduled to run by the system, or has terminated.
	 * If the returned array is of non-zero length then the first element of
	 * the array represents the top of the stack, which is the most recent
	 * method invocation in the sequence.  The last element of the array
	 * represents the bottom of the stack, which is the least recent method
	 * invocation in the sequence.
	 *
	 * <p>If there is a security manager, and this thread is not
	 * the current thread, then the security manager's
	 * <tt>checkPermission</tt> method is called with a
	 * <tt>RuntimePermission("getStackTrace")</tt> permission
	 * to see if it's ok to get the stack trace.
	 *
	 * <p>Some virtual machines may, under some circumstances, omit one
	 * or more stack frames from the stack trace.  In the extreme case,
	 * a virtual machine that has no stack trace information concerning
	 * this thread is permitted to return a zero-length array from this
	 * method.
	 *
	 * @return an array of <tt>StackTraceElement</tt>,
	 * each represents one stack frame.
	 * @throws SecurityException if a security manager exists and its
	 *                           <tt>checkPermission</tt> method doesn't allow
	 *                           getting the stack trace of thread.
	 * @see SecurityManager#checkPermission
	 * @see RuntimePermission
	 * @see Throwable#getStackTrace
	 * @since 1.5
	 */
	public StackTraceElement[] getStackTrace()
	{
		if (this != Thread.currentThread())
		{
			// check for getStackTrace permission
			SecurityManager security = System.getSecurityManager();
			if (security != null)
			{
				security.checkPermission(SecurityConstants.GET_STACK_TRACE_PERMISSION);
			}
			// optimization so we do not call into the vm for threads that
			// have not yet started or have terminated
			if (!isAlive())
			{
				return EMPTY_STACK_TRACE;
			}
			StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[]{this});
			StackTraceElement[] stackTrace = stackTraceArray[0];
			// a thread that was alive during the previous isAlive call may have
			// since terminated, therefore not having a stacktrace.
			if (stackTrace == null)
			{
				stackTrace = EMPTY_STACK_TRACE;
			}
			return stackTrace;
		} else
		{
			// Don't need JVM help for current thread
			return (new Exception()).getStackTrace();
		}
	}

	/**
	 * Returns a map of stack traces for all live threads.
	 * The map keys are threads and each map value is an array of
	 * <tt>StackTraceElement</tt> that represents the stack dump
	 * of the corresponding <tt>Thread</tt>.
	 * The returned stack traces are in the format specified for
	 * the {@link #getStackTrace getStackTrace} method.
	 *
	 * <p>The threads may be executing while this method is called.
	 * The stack trace of each thread only represents a snapshot and
	 * each stack trace may be obtained at different time.  A zero-length
	 * array will be returned in the map value if the virtual machine has
	 * no stack trace information about a thread.
	 *
	 * <p>If there is a security manager, then the security manager's
	 * <tt>checkPermission</tt> method is called with a
	 * <tt>RuntimePermission("getStackTrace")</tt> permission as well as
	 * <tt>RuntimePermission("modifyThreadGroup")</tt> permission
	 * to see if it is ok to get the stack trace of all threads.
	 *
	 * @return a <tt>Map</tt> from <tt>Thread</tt> to an array of
	 * <tt>StackTraceElement</tt> that represents the stack trace of
	 * the corresponding thread.
	 * @throws SecurityException if a security manager exists and its
	 *                           <tt>checkPermission</tt> method doesn't allow
	 *                           getting the stack trace of thread.
	 * @see #getStackTrace
	 * @see SecurityManager#checkPermission
	 * @see RuntimePermission
	 * @see Throwable#getStackTrace
	 * @since 1.5
	 */
	public static Map<Thread, StackTraceElement[]> getAllStackTraces()
	{
		// check for getStackTrace permission
		SecurityManager security = System.getSecurityManager();
		if (security != null)
		{
			security.checkPermission(SecurityConstants.GET_STACK_TRACE_PERMISSION);
			security.checkPermission(SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
		}

		// Get a snapshot of the list of all threads
		Thread[] threads = getThreads();
		StackTraceElement[][] traces = dumpThreads(threads);
		Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
		for (int i = 0; i < threads.length; i++)
		{
			StackTraceElement[] stackTrace = traces[i];
			if (stackTrace != null)
			{
				m.put(threads[i], stackTrace);
			}
			// else terminated so we don't put it in the map
		}
		return m;
	}


	private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION = new RuntimePermission("enableContextClassLoaderOverride");

	/**
	 * cache of subclass security audit results
	 */
	/* Replace with ConcurrentReferenceHashMap when/if it appears in a future
	 * release */
	private static class Caches
	{
		/**
		 * cache of subclass security audit results
		 */
		static final ConcurrentMap<WeakClassKey, Boolean> subclassAudits = new ConcurrentHashMap<>();

		/**
		 * queue for WeakReferences to audited subclasses
		 */
		static final ReferenceQueue<Class<?>> subclassAuditsQueue = new ReferenceQueue<>();
	}

	/**
	 * Verifies that this (possibly subclass) instance can be constructed
	 * without violating security constraints: the subclass must not override
	 * security-sensitive non-final methods, or else the
	 * "enableContextClassLoaderOverride" RuntimePermission is checked.
	 */
	private static boolean isCCLOverridden(Class<?> cl)
	{
		if (cl == Thread.class) return false;

		processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
		WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
		Boolean result = Caches.subclassAudits.get(key);
		if (result == null)
		{
			result = Boolean.valueOf(auditSubclass(cl));
			Caches.subclassAudits.putIfAbsent(key, result);
		}

		return result.booleanValue();
	}

	/**
	 * Performs reflective checks on given subclass to verify that it doesn't
	 * override security-sensitive non-final methods.  Returns true if the
	 * subclass overrides any of the methods, false otherwise.
	 */
	private static boolean auditSubclass(final Class<?> subcl)
	{
		Boolean result = AccessController.doPrivileged(new PrivilegedAction<Boolean>()
		{
			public Boolean run()
			{
				for (Class<?> cl = subcl; cl != Thread.class; cl = cl.getSuperclass())
				{
					try
					{
						cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]);
						return Boolean.TRUE;
					} catch (NoSuchMethodException ex)
					{
					}
					try
					{
						Class<?>[] params = {ClassLoader.class};
						cl.getDeclaredMethod("setContextClassLoader", params);
						return Boolean.TRUE;
					} catch (NoSuchMethodException ex)
					{
					}
				}
				return Boolean.FALSE;
			}
		});
		return result.booleanValue();
	}

	private native static StackTraceElement[][] dumpThreads(Thread[] threads);

	private native static Thread[] getThreads();

	/**
	 * Returns the identifier of this Thread.  The thread ID is a positive
	 * <tt>long</tt> number generated when this thread was created.
	 * The thread ID is unique and remains unchanged during its lifetime.
	 * When a thread is terminated, this thread ID may be reused.
	 *
	 * @return this thread's ID.
	 * @since 1.5
	 */
	public long getId()
	{
		return tid;
	}

	/**
	 * A thread state.  A thread can be in one of the following states:
	 * <ul>
	 * <li>{@link #NEW}<br>
	 *     A thread that has not yet started is in this state.
	 *     </li>
	 * <li>{@link #RUNNABLE}<br>
	 *     A thread executing in the Java virtual machine is in this state.
	 *     </li>
	 * <li>{@link #BLOCKED}<br>
	 *     A thread that is blocked waiting for a monitor lock
	 *     is in this state.
	 *     </li>
	 * <li>{@link #WAITING}<br>
	 *     A thread that is waiting indefinitely for another thread to
	 *     perform a particular action is in this state.
	 *     </li>
	 * <li>{@link #TIMED_WAITING}<br>
	 *     A thread that is waiting for another thread to perform an action
	 *     for up to a specified waiting time is in this state.
	 *     </li>
	 * <li>{@link #TERMINATED}<br>
	 *     A thread that has exited is in this state.
	 *     </li>
	 * </ul>
	 *
	 * <p>
	 * A thread can be in only one state at a given point in time.
	 * These states are virtual machine states which do not reflect
	 * any operating system thread states.
	 *
	 * @see #getState
	 * @since 1.5
	 */
	public enum State
	{
		/**
		 * Thread state for a thread which has not yet started.
		 */
		NEW,

		/**
		 * Thread state for a runnable thread.  A thread in the runnable
		 * state is executing in the Java virtual machine but it may
		 * be waiting for other resources from the operating system
		 * such as processor.
		 */
		RUNNABLE,

		/**
		 * Thread state for a thread blocked waiting for a monitor lock.
		 * A thread in the blocked state is waiting for a monitor lock
		 * to enter a synchronized block/method or
		 * reenter a synchronized block/method after calling
		 * {@link Object#wait() Object.wait}.
		 */
		BLOCKED,

		/**
		 * Thread state for a waiting thread.
		 * A thread is in the waiting state due to calling one of the
		 * following methods:
		 * <ul>
		 *   <li>{@link Object#wait() Object.wait} with no timeout</li>
		 *   <li>{@link #join() Thread.join} with no timeout</li>
		 *   <li>{@link LockSupport#park() LockSupport.park}</li>
		 * </ul>
		 *
		 * <p>A thread in the waiting state is waiting for another thread to
		 * perform a particular action.
		 * <p>
		 * For example, a thread that has called <tt>Object.wait()</tt>
		 * on an object is waiting for another thread to call
		 * <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
		 * that object. A thread that has called <tt>Thread.join()</tt>
		 * is waiting for a specified thread to terminate.
		 */
		WAITING,

		/**
		 * Thread state for a waiting thread with a specified waiting time.
		 * A thread is in the timed waiting state due to calling one of
		 * the following methods with a specified positive waiting time:
		 * <ul>
		 *   <li>{@link #sleep Thread.sleep}</li>
		 *   <li>{@link Object#wait(long) Object.wait} with timeout</li>
		 *   <li>{@link #join(long) Thread.join} with timeout</li>
		 *   <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
		 *   <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
		 * </ul>
		 */
		TIMED_WAITING,

		/**
		 * Thread state for a terminated thread.
		 * The thread has completed execution.
		 */
		TERMINATED;
	}

	/**
	 * Returns the state of this thread.
	 * This method is designed for use in monitoring of the system state,
	 * not for synchronization control.
	 *
	 * @return this thread's state.
	 * @since 1.5
	 */
	public State getState()
	{
		// get current thread state
		return sun.misc.VM.toThreadState(threadStatus);
	}

	// Added in JSR-166

	/**
	 * Interface for handlers invoked when a <tt>Thread</tt> abruptly
	 * terminates due to an uncaught exception.
	 * <p>When a thread is about to terminate due to an uncaught exception
	 * the Java Virtual Machine will query the thread for its
	 * <tt>UncaughtExceptionHandler</tt> using
	 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
	 * <tt>uncaughtException</tt> method, passing the thread and the
	 * exception as arguments.
	 * If a thread has not had its <tt>UncaughtExceptionHandler</tt>
	 * explicitly set, then its <tt>ThreadGroup</tt> object acts as its
	 * <tt>UncaughtExceptionHandler</tt>. If the <tt>ThreadGroup</tt> object
	 * has no
	 * special requirements for dealing with the exception, it can forward
	 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
	 * default uncaught exception handler}.
	 *
	 * @see #setDefaultUncaughtExceptionHandler
	 * @see #setUncaughtExceptionHandler
	 * @see ThreadGroup#uncaughtException
	 * @since 1.5
	 */
	@FunctionalInterface
	public interface UncaughtExceptionHandler
	{
		/**
		 * Method invoked when the given thread terminates due to the
		 * given uncaught exception.
		 * <p>Any exception thrown by this method will be ignored by the
		 * Java Virtual Machine.
		 *
		 * @param t the thread
		 * @param e the exception
		 */
		void uncaughtException(Thread t, Throwable e);
	}

	// null unless explicitly set
	private volatile UncaughtExceptionHandler uncaughtExceptionHandler;

	// null unless explicitly set
	private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;

	/**
	 * Set the default handler invoked when a thread abruptly terminates
	 * due to an uncaught exception, and no other handler has been defined
	 * for that thread.
	 *
	 * <p>Uncaught exception handling is controlled first by the thread, then
	 * by the thread's {@link ThreadGroup} object and finally by the default
	 * uncaught exception handler. If the thread does not have an explicit
	 * uncaught exception handler set, and the thread's thread group
	 * (including parent thread groups)  does not specialize its
	 * <tt>uncaughtException</tt> method, then the default handler's
	 * <tt>uncaughtException</tt> method will be invoked.
	 * <p>By setting the default uncaught exception handler, an application
	 * can change the way in which uncaught exceptions are handled (such as
	 * logging to a specific device, or file) for those threads that would
	 * already accept whatever &quot;default&quot; behavior the system
	 * provided.
	 *
	 * <p>Note that the default uncaught exception handler should not usually
	 * defer to the thread's <tt>ThreadGroup</tt> object, as that could cause
	 * infinite recursion.
	 *
	 * @param eh the object to use as the default uncaught exception handler.
	 *           If <tt>null</tt> then there is no default handler.
	 * @throws SecurityException if a security manager is present and it
	 *                           denies <tt>{@link RuntimePermission}
	 *                           (&quot;setDefaultUncaughtExceptionHandler&quot;)</tt>
	 * @see #setUncaughtExceptionHandler
	 * @see #getUncaughtExceptionHandler
	 * @see ThreadGroup#uncaughtException
	 * @since 1.5
	 */
	public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh)
	{
		SecurityManager sm = System.getSecurityManager();
		if (sm != null)
		{
			sm.checkPermission(new RuntimePermission("setDefaultUncaughtExceptionHandler"));
		}

		defaultUncaughtExceptionHandler = eh;
	}

	/**
	 * Returns the default handler invoked when a thread abruptly terminates
	 * due to an uncaught exception. If the returned value is <tt>null</tt>,
	 * there is no default.
	 *
	 * @return the default uncaught exception handler for all threads
	 * @see #setDefaultUncaughtExceptionHandler
	 * @since 1.5
	 */
	public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler()
	{
		return defaultUncaughtExceptionHandler;
	}

	/**
	 * Returns the handler invoked when this thread abruptly terminates
	 * due to an uncaught exception. If this thread has not had an
	 * uncaught exception handler explicitly set then this thread's
	 * <tt>ThreadGroup</tt> object is returned, unless this thread
	 * has terminated, in which case <tt>null</tt> is returned.
	 *
	 * @return the uncaught exception handler for this thread
	 * @since 1.5
	 */
	public UncaughtExceptionHandler getUncaughtExceptionHandler()
	{
		return uncaughtExceptionHandler != null ? uncaughtExceptionHandler : group;
	}

	/**
	 * Set the handler invoked when this thread abruptly terminates
	 * due to an uncaught exception.
	 * <p>A thread can take full control of how it responds to uncaught
	 * exceptions by having its uncaught exception handler explicitly set.
	 * If no such handler is set then the thread's <tt>ThreadGroup</tt>
	 * object acts as its handler.
	 *
	 * @param eh the object to use as this thread's uncaught exception
	 *           handler. If <tt>null</tt> then this thread has no explicit handler.
	 * @throws SecurityException if the current thread is not allowed to
	 *                           modify this thread.
	 * @see #setDefaultUncaughtExceptionHandler
	 * @see ThreadGroup#uncaughtException
	 * @since 1.5
	 */
	public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh)
	{
		checkAccess();
		uncaughtExceptionHandler = eh;
	}

	/**
	 * Dispatch an uncaught exception to the handler. This method is
	 * intended to be called only by the JVM.
	 */
	private void dispatchUncaughtException(Throwable e)
	{
		getUncaughtExceptionHandler().uncaughtException(this, e);
	}

	/**
	 * Removes from the specified map any keys that have been enqueued
	 * on the specified reference queue.
	 */
	static void processQueue(ReferenceQueue<Class<?>> queue, ConcurrentMap<? extends WeakReference<Class<?>>, ?> map)
	{
		Reference<? extends Class<?>> ref;
		while ((ref = queue.poll()) != null)
		{
			map.remove(ref);
		}
	}

	/**
	 * Weak key for Class objects.
	 **/
	static class WeakClassKey extends WeakReference<Class<?>>
	{
		/**
		 * saved value of the referent's identity hash code, to maintain
		 * a consistent hash code after the referent has been cleared
		 */
		private final int hash;

		/**
		 * Create a new WeakClassKey to the given object, registered
		 * with a queue.
		 */
		WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue)
		{
			super(cl, refQueue);
			hash = System.identityHashCode(cl);
		}

		/**
		 * Returns the identity hash code of the original referent.
		 */
		@Override
		public int hashCode()
		{
			return hash;
		}

		/**
		 * Returns true if the given object is this identical
		 * WeakClassKey instance, or, if this object's referent has not
		 * been cleared, if the given object is another WeakClassKey
		 * instance with the identical non-null referent as this one.
		 */
		@Override
		public boolean equals(Object obj)
		{
			if (obj == this) return true;

			if (obj instanceof WeakClassKey)
			{
				Object referent = get();
				return (referent != null) && (referent == ((WeakClassKey) obj).get());
			} else
			{
				return false;
			}
		}
	}


	// The following three initially uninitialized fields are exclusively
	// managed by class java.util.concurrent.ThreadLocalRandom. These
	// fields are used to build the high-performance PRNGs in the
	// concurrent code, and we can not risk accidental false sharing.
	// Hence, the fields are isolated with @Contended.

	/**
	 * The current seed for a ThreadLocalRandom
	 */
	@sun.misc.Contended("tlr")
	long threadLocalRandomSeed;

	/**
	 * Probe hash value; nonzero if threadLocalRandomSeed initialized
	 */
	@sun.misc.Contended("tlr")
	int threadLocalRandomProbe;

	/**
	 * Secondary seed isolated from public ThreadLocalRandom sequence
	 */
	@sun.misc.Contended("tlr")
	int threadLocalRandomSecondarySeed;

	/* Some private helper methods */
	private native void setPriority0(int newPriority);

	private native void stop0(Object o);

	private native void suspend0();

	private native void resume0();

	private native void interrupt0();

	private native void setNativeName(String name);
}
